IL‐10 production by CD4+CD25+ allergen‐specific Tr1 (regulatory T) cells, B cells and monocytes induces and correlates with the production of IgG4 and the increase in IgG4/IgE ratio in allergen and peptide immunotherapies in allergy and autoimmune diseases 60, 61, 62 and are thought to underlie the induction of tolerance to allergens 63. This evidence concerns the gene CD4 and allergic disease.